Dielectric porcelain composition

ABSTRACT

A dielectric porcelain composition comprising a sintered product composed of above 2% by weight but below 31% by weight of lead titanate (PbTiO3), above 35% by weight but below 83% by weight of strontium titanate (SrTiO3), above 3% by weight but below 19.1% by weight of bismuth oxide (Bi2O3) above 0.5% by weight but below 18% by weight of titanium oxide (TiO2) and above 2.8% by weight but below 20.1% by weight of calcium titanate (CaTiO3), the weight ratio of titanium oxide (TiO2) to bismuth oxide (Bi2O3) being between 0.2 and 2.0.

United States Patent [191 Yamaoka et al.

[Ill 3,869,398 Mar. 4, 1975 Yasunori Takahashi, Tokyo, both of 3 Japan [73] Assignees: Taiyo Yuden Kabushiki Kaish; Sony Corporation, both of Tokyo, Japan [22] Filed: Aug. 23, 1973 [21] Appl. No.: 390,948

[30] Foreign Application Priority Data Sept. 20, 1972 Japan 47-93697 [52] U.S. Cl 252/635, 252/629, 106/46, l06/73.3 [51] Int. Cl. H01b 3/02 [58] Field of Search 252/635, 62.9; 106/73.3, 106/46, 39.8

[56] References Cited UNITED STATES PATENTS 2,369,327 2/1945 Wainer l06/DIG. 5 FOREIGN PATENTS OR APPLICATIONS 920,738 3/1963 Great Britain 252/635 246,677 6/1969 'U.S S.R 252/635 OTHER PUBLICATIONS Ekeda et a1, Piezoelectric Properties of Pb(Zr- Ti)O 2/64, pp. 63-71 Japanese Journal of Applied Physics, Vol. 3, 2 copy in 252/629 Primary Examiner-Maynard R. Wilbur Assistant Examiner-N. Moskowitz Attorney, Agent, or Firm-Waters, Roditi, Schwartz & Nissen [57] ABSTRACT A dielectric porcelain composition comprising a sintered product composed of above 2% by weight but below 31% by weight of lead titanate (PbTiO above 35% by weight but below 83% by weight of strontium titanate (SrTiO above 3% by weight but below 19.1% by weight of bismuth oxide (Bi- 0 above 0.5% by weight but below 18% by weight of titanium oxide (TiO and above 2.8% by weight but below 20.l% by weight of calcium titanate (CaTiO the weight ratio of titanium oxide (TiO to bismuth oxide (B30 being between 0.2 and 2.0.

1 Claim, 3 Drawing Figures PATENTEBHAR "41975 3.869398 51 DC XM E 6 q FF POWER SOURC I DIELECTRIC PORCELAIN COMPOSITION BACKGROUND a. Field of the Invention 2 BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a circuit diagram showing a'circuit for measuring electrical and mechanical coupling coefficients, FIG. 2 is a graph showing the voltage dependence T i p p relates to dlelepmf: pqrcelalli property of the dielectric constant of various composiposition which is comparatively high in dielectric con- (ms and i z f j g itlrpperty Small m FIG. 3 is a circuit diagram showing a circuit for a v0 epen ence o e ec cons an charging and discharging test cycle.

b. Prior Art A high dielectric constant porcelain having a dielec- DESCRIPTION OF THE PREFERRED tric constant of at least 1000 of barium titante type has EMBODIMENTS li s T :2 a grtacncal ih Samples of various blending compositions by weight 1 f i I antate i g Ti as shown in Table l were respectively prepared in acl 5. no 9 prtoperyyvnen f i l5 cordance with conventional ceramic manufacturing V0 l especllla y i O processes. Each composition was prepared by mixing a zi g ls z z g a z g ii and grinding the mixture and then it was molded under g th I 22: ic g i Li 3 z g 1 pressure and sintered in a furnace with an air atmora id b d wn or risonalrlncensound or a sphere at a temperature of 1200-l300C to obtain a l k e owin to mechzmic 1 sample 4 mm in thickness and 20 mm in diameter. 8 g z z kmfwn thatgthe barium Then, for each of these samples, there were measured t orlcelgin Z 3 lat e decrease in electro the dielectric constant, tan 6, the electrical and meg g i for 10a d v M egbut no im rovements chanical coupling coefficient Kp, the break-down voltf g d o g p age and the bias property. The electrical and mechaniereo ave ma cal coupling coefficient is a value which is measured In order to obviate dificiencies associated with barunder the condition that a larizati. tre tm t b ium titanate ceramic dielectrics, the present invention p0 on a en y a have reviousl r0 osed a orcelain dielectric com oknown process Is not applied to the Sample before measitionpof PbTig p SrpTiO 5 and Tio p suring and a bias voltage of direct current of 3 Kv/mm 2 is applied thereto at the time of measuring. FIG. 1 shows a circuit for measuring this properly, and in this SUMMARY OF THE INVENTION circuit a resonant frequency (f and an anti-resonant frequency (f are measured from a voltage value of a v valve voltmeter (V) by an oscillation frequency, and The invention is directed specifically to a high volt- Kp i calculated from the following formula: age and high capacity porcelain condenser, character- Y ized in that it comprises a sintered product compound KP K (f1 Pom of above 2% by weight but below 31% by weight of lead where, K is a constant depending on the vibration titanate (PbTlO above 35% by weight but below 83% mode. The bias property is calculated from the followby weight of strontium titante (SrTiO above 3% by ing formula: weight but below 19.1% by weight of bismuth oxide (Bi O above 0.5% by weight but below 18% by weight Co/Co X 100 of titanium oxide (T10 and above 2.8% by weight but where, C is the electrostatic capacity at the time of apbelow 20.1% by weight of calcium titanate (CaTiO plication ofa bias voltage ofdirect current of3 Kv/mm, the weight ratio of titanium oxide (TiO to bismuth and C is the electrostatic capacity at the time of zero oxide (B1 0 being between 0.2 and 2.0. bias.

Table 1 Composition (weight Sample No SrTiO PbTiO CaTiO B1203 T102 TiO Bi O x 1 83 6 5 5 0.2 2 8 6 5 11 0.2 x 3 71 2 5 7.8 14.2 1.8

4 62.4 5 5 18.5 9.1 0.49 x 5 60.0 16.1 0 16.1 7.8 0.48 x 6 58.2 15.6 2.8 15.6 7.8 0.5 7 57.2 15.3 4.6 15.3 7.6 0.5 8 55.7 14.9 7.1 14.9 7.4 0.5 9 54.6 14.7 8.8 14.7 7.2 0.49 10 53.7 14.4 10.3 14.4 7.2 0.50 11 52.7 14.2 11.9 14.2 7.0 0.49 X 12 45.0 23.0 7.1 19.1 5.8 0.30 13 43.6 24.4 9.1 17.3 5.6 0.32 14 38.2 26.4 12.1 17.3 6.0 0.34 15 42.0 23.6 13.5 15.5 5.4 0.35 16 39.6 22.1 19.1 14.0 5.1 0.36 X 17 40.0 22.0 20.1 12.8 5.1 0.40 x 18 36.4 31.0 9.0 17.3 5.6 0.32 x 19 79.0 12.0 5.0 3.0 1.0 0.33

20 53.6 13.6 7.3 12.7 12.8 1.0 X 21 50.0 12.6 6.0 13.4 18.0 1.3 X 22 35.0 20.0 19.0 16.0 10.0 0.62 X 23 76.0 10.0 7.5 6.0 0.5 0.08

3 4 Properties Sample Dielectric Tan 8 Kp Breakdown Bias No. constant voltage (Kv/mm) 2 1070 0.05 2.9 15 7.5 X 3 750 0.05 2.5 14 --5.5 4 1100 0.05 2.4 18 3.1 X 5 2200 0.05 6.6 12 20.0 X 6 2000 0.05 5.8 14 15.0 7 1900 0.05 4.4 16 9.0 8 1800 0.1 3.5 16 5.0 9 1650 0.1 4.8 18 2.5 10 1400 0.1 2.9 18 0.5 11 1300 0.1 2.0 18 105 X 12 2000 4.5 10.1 11 15.7 13 1750 2.0 3.8 13 5.7 14 1350 0.6 3.5 13 0.95 15 1150 0.6 3.0 14 +2.83 16 1050 0.3 2.9 l8 +3.50 X 17 850 0.3 2.5 18 +4.0 X 18 2500 8.4 15.0 8 sintering insufficient X 19 900 0.1 3.1 14 -8.1

20 1200 r 0.1 3.0 14 8.5 X 21 950 0.1 3.5 14 -l0.5 X 22 870 0.3 5.0 13 3.5 X 23 750 0.5 2.8 13 8.2 24 1080 0.1 3.0 15 4.5 X 25 820 0.05 2.4 15 5.0

Referring to Table 1, if SrTiO is 83% or more and 35% or less as in samples Nos. 1 and 22, the dielectric constant is below 1000 which renders the condensor inadequate. lf PbTiO is 2% or less as in sample No. 3, the dielectric constant is similarly lowered, and if it is 31% or more as in sample No. 18, the dielectric constant is high but tan 8 and the electrical and mechanical coupling coefficient Kp are excessively large and additionally the breakdown voltage is also lowered and the sintering property is insufficient. If CaTiO is 2.8% or less as in samples 5 and 6, the bias property is not improved, and if it is 20.1% or more as in sample No. 17, the dielectric constant is lowered. If B1203 is 3% or less as in sample No. 19, the dielectric constant is lowered, and if it is 19.1% or more as in sample No. 12, tan 8 is large and also the bias property is not improved. If TiO- bismuth oxide, titanium oxide and calcium titanate are composed within the foregoing respective ranges, and thereby it is possible to obtain such a product whose dielectric constant is 1000 or more, Kp is 10% or less, the breakdown voltage is 13 Kv/mm or more and the bias property is from 10% to +3%.

It can be assumed that the improvement in the electrical and mechanical coupling cofficient Kp and the bias property is chiefly due to the action of CaTiO though the mechanism thereof is not yet understood. As shown in Table 2, compositions of SrTiO PbTiO B1 0 TiO mixed in predetermined constant amounts are respectively mixed with different amounts of CaTiO so as to form the indicated respective samples of 100% by weight and the influence of the added CaTiO is measured.

Table 2 Composition (weight Properties Sample SiTiO PbTiO B1 0 TiO CaTiO Dielectan 8 Kp Bias No. (22%) (13.5%) (4.5%) tric constant 26 I00 0 0 2500 0.10 7.5 -l 1.8 27 97 3 3 2200 0.05 6.0 7.5 28 95 5 5 2000 0.05 5.8 4.0 29 90 l0 10 I800 0.5 4.7 2.0 30 87 l3 13 1500 0.5 3.0 0.4

is 0.5% or lessas in sample No. 23 or is 18.0% or more as in sample No. 21, the dielectric constant is lower than 1000 and hence unacceptable. Additionally, if the ratio of Ti0 to Bi O is above 2.0 as in sample No. 25, the dielectric constant becomes lower than 1000. If this ratio is below 0.2, sintering is difficult and a fine porcelain cannot be obtained.

The dielectric porcelain composition of the invention is characterized in that lead titanate, strontium titanate,

From Table 2, it will be clear that by the addition of 60 CaTiO the dielectric constant has a somewhat lowercelain composition of the invention is excellent in values of breakdown voltage, and it is superior to the known material also in the charging and discharging test. Namely, in the case when, for example, in a circuit as shown in FIG. 3 a test product is supplied with a rated direct current voltage (3 Kv/mm in the case) and charging and discharging are repeated, the product of the invention, i.e. sample No. 11 does not break down even after 100,000 cycles. In FIG. 3, Cx designates the condenser to be tested, Co is an electric charge supplying condenser, Y is a circuit protecting resistor and S is a switch.

Thus, a condenser with the dielectric porcelain composition of the invention exhibits characteristic features especially in a high voltage circuit, and when compared with the conventional high dielectric constant porcelain of barium titanate type, is high in initial stage breakdown voltage and at the same time is small in the electric distortion property. Hence, the troubles caused by the known porcelain in a high voltage circuit are diminished and its deterioration during its use is extremely reduced as shown in the charging and discharging test. Accordingly, an elememt which is smaller in thickness than that of the conventional material can withstand the predetermined use voltage, and therefore the electrostatic capacity per unit of electrode area becomes large in reverse proportion thereto, and since the voltage dependence property of the dielectric constant is extremely small, it is not necessary that a high initial electrostatic capacity value be used in expectation of capacity decrease. Thus, by the mutual cooperation of these effects, a result is obtained in which the volume of a ceramic body can be reduced to from 1/10 to 1/15 in comparison with that of the barium titanate type porcelain for the same use.

What is claimed is:

l. A dielectric porcelain composition comprising a sintered product consisting essentially of above 2% by weight but below 31% by weight of lead titanate (PbTiO above 35% by weight but below 83% by weight of strontium titante (SrTiO above 3% by weight but below 19.1% by weight of bismuth oxide E 0, above 0.5% by weight but below 18% by weight of titanium oxide (TiO and above 2.8% by weight but below 20.1% by weight of calcium titanate (CaTiO the weight ratio of titanium oxide (TiO to bismuth oxide (Bi O being between 0.2 and 2.0. 

1. A DIELECTRIC PORECLAIN COMPOSITION COMPRISING A SINTERED PRODUCT CONSISTING ESSENTIALLY OF ABOVE 2% BY WEIGHT BUT BELOW 31% BY WEIGHT OF LEAD TITANATE (PBTIO3), ABOVE 35% BY WEIGHT BUT BELOW 83% BY WEIGHT BOF STROMTIUM TITANTE (SRTIO3), ABOVE 3% BY WEIGHT BUT BELOW 19.1% BY WEIGHT OF BISMUTH OXIDE (BI2O3), ABOVE 0.5% BY WEIGHT BUTYL BELOW 18% BY WEIGHT OF TITANIUM OXIDE (TIO2) AND ABOVE 2.8% BY WEIGHT BUT BELOW 20.1% BY WEIGHT OF CALCIUM TITANATE (CATIO3), THE WEIGHT RATIO OF TITANIUM OXIDE (TIO2) TO BISMUTH OXIDE (BI2O3) BEING BETWEEN 0.2 AND 2.0 